The diagram given below depicts a defect of the human eye which has been corrected by using a suitable lens. Answer the following questions: The diagram given below depicts a defect of the human eye which has been corrected by using a suitable lens. Answer the following questions:
Name the defect that has been corrected. Which type of lens has been used for the correction?
Topic: Myopia and its correction
Answer
The defect is MYOPIA (short-sightedness). It has been corrected using a CONCAVE (diverging) LENS.
Identify the defect from the SHAPE OF THE LENS in the diagram: a lens thin in the middle and thicker at the edges is CONCAVE, and a concave lens corrects MYOPIA.
HOW IT WORKS: in myopia the eye bends light too strongly, so the image would form IN FRONT of the retina. A concave lens DIVERGES the rays slightly before they enter, so the focus is pushed BACK onto the retina.
The pair to learn together: MYOPIA — image IN FRONT of the retina — CONCAVE lens HYPERMETROPIA — image BEHIND the retina — CONVEX lens
By shape: a concave lens spreads rays apart, a convex lens brings them together. If the focus is forming too early, you need to spread the rays.